1. Field of the Invention
The present invention relates to a wood bleaching and cleaning composition and, more particular, to aqueous formulations containing non-hazardous components for restoring the original color to degraded wood surfaces.
2. Description of the Prior Art
The original color and texture of wood surfaces which are intended to present a esthetically natural appearance are often lost upon extended exposure to environmental conditions. After prolonged periods of exposure to ultraviolet light, moisture, pollution and temperature extremes, for example, surfaces of wood articles and constructions eventually deteriorate in coloration or become unsightly stained. Stains from other than exposure to long term weathering which may accumulate on the outer surface of wood structures are usually due to dirt, mold, mildew and tannin residues. In many instances, refinishing or restoration of these weathered and/or stained wood structures becomes the only viable option since the replacement costs involved would be economically prohibitive. However, commercial refinishing processes which include such abrasive cleaning techniques as sending the entire wood surface in order to remove the discolored area are costly and time-consuming operations. Of course, merely painting this damaged area by applying a pigmented film onto the wood surface does not result in a coating finish that remotely approaches the original wood appearance. Moreover, such paint coatings usually undergo severe discoloration under the influence of environmental exposure and the film coatings themselves are subject to cracking, followed by peeling and blistering in a relatively short period of time.
Efforts to improve the appearance of discolored wood surfaces have also included the use of a wide variety of bleaching and/or cleaning agents. For instance, chlorine-based chemicals such as chlorine, chlorine dioxide and hypochlorite have been used in the prior art to bring about a chemical bleaching of the wood fibers. However, these bleaching agents produce chlorides and chlorinated organic compounds which are highly toxic and have an undersirable impact on the environment. Moreover, such agents as chlorine dioxide are highly corrosive, explosive and require expert handling with highly specialized equipment to avoid serious injury to the handler.
It has been proposed to reduce or eliminate undesirable chlorinated compounds in wood bleaching processes by substituting non-chlorine bleaching agents such as peroxides, ozone, paracetic acid, oxalic acid, etc., for the chlorine-based bleaching chemicals. Unfortunately, no chlorine-free wood bleaching procedure has been efficiently developed which is capable of safely producing brightened wood surfaces without significantly degrading the wood's mechanical properties.
Another alternative that has been proposed or practiced in an effort to remove the discoloration of weathered or stained wood surfaces is to apply a nonabrasive, liquid cleaning composition. However, among the host of commercial and industrial liquid cleaners generally containing various combinations of surfactants and alkaline salts and/or acids, many of them have met with only varying degrees of success and none have proved to be safe and effective in removing discolored deposits on wood surfaces at an acceptable cost. For instance, U.S. Pat. No. 3,211,659 to Pikaar describes an aqueous solution of non-toxic acid such as citric acid, phosphoric acid and acetic acid, a buffering reagent and a wetting agent for the removal of various contaminants from the surface of shell eggs. While this prior art acid composition is relatively mild and safe, it clearly lacks sufficient strength to remove embedded soil and resistant stains on wood surfaces resulting from exposure to long term weathering.